Temp fix for booked plugin (line 47)

shortcodes.php

$atts = shortcode_atts(
			array(
				'size' => 'large',
				'calendar' => false,
				'year' => false,
				'month' => false,
				'switcher' => false,
				'post_id' => false
			), $atts );
		
		ob_start();
		echo '<div id="data-ajax-url">'.get_the_permalink($atts['post_id']).'</div>';